In connection with so-called jump-lifts, the bottom part of an elevator hoistway is taken into use already before the building has been completed. In this case the top part of the elevator hoistway can be constructed at the same time as an elevator moving in the bottom part of the elevator hoistway already serves people on the lower floors of the building. Generally in jump-lifts the elevator car moving in the lower parts of the elevator hoistway is supported and moved during construction-time use with a hoisting machine supported on a platform in the elevator hoistway. The installation work in the parts of the elevator hoistway above this machine room platform is performed from a movable platform or corresponding in the elevator hoistway, which installation work comprises, among other things, the installation of guide rails and electrification in the elevator hoistway. When the elevator hoistway under construction above the machine room platform has reached a sufficient stage of completion, the completed part of the elevator hoistway can be taken into use. In this case a jump-lift is performed, wherein the machine room platform is raised to a higher level in the elevator hoistway. A worksite crane used in the construction of the building has conventionally been used for the lifting. One problem with this type of arrangement is that the worksite crane is not always available when needed. Another problem is that the elevator hoistway must be open at its top end so that the hook of the worksite crane that is on the roof of the building can be lowered into the hoistway. When the elevator hoistway has reached its final height, a machine room has conventionally been built at the end of the elevator hoistway and after that the final machinery of the elevator has been brought there. Thus to support the final machinery it has been necessary to construct a structure above the elevator hoistway from scratch. Another problem has been that a separate final machinery has been needed in addition to the construction-time machinery. Otherwise the final phase would have been complex and slow to perform, and the time during which the elevator is out of use would be long.
The weight of the machine room platforms combined with the weight of the parts of the elevator supported by the machine room has increased owing to, among other things, buildings that are taller than before. Owing to the very great travel heights of modern elevators, the machine size and rope masses, among other things, are so great that the hoisting capacity needed to perform the last jump-lifts is large. For the same reason, the support needed for the lifting must be robustly made. Finding advantageous support, particularly in the final phase of the manufacturing process, has been a problem, and it has been necessary to use complex solutions or a worksite crane.